Method of making acrylic acid from hydroxypropionic acid

Abstract

Methods for making acrylic acid, acrylic acid derivatives, or mixtures thereof by contacting a stream containing hydroxypropionic acid, hydroxypropionic acid derivatives, or mixtures thereof with either an active catalyst containing an amorphous and partially-dehydrated phosphate salt or a precursor catalyst containing a crystalline phosphate salt in a reactor with a low corrosion rate are provided.

What is claimed is: 
     
       1. A method of making acrylic acid, acrylic acid derivatives, or mixtures thereof comprising contacting a gas feed stream comprising water vapor and hydroxypropionic acid, hydroxypropionic acid derivatives, or mixtures thereof with a catalyst in a bi-layer reactor at a temperature, a water partial pressure, a GHSV, and a WHSV to dehydrate said hydroxypropionic acid, hydroxypropionic acid derivatives, or mixtures thereof, resulting in the production of acrylic acid, acrylic acid derivatives, or mixtures thereof; wherein said catalyst comprises a phosphate salt comprising a cation and an anion represented by the empirical formula:
   [H 2(1−x) PO (4−x) ] −   
 wherein x is any real number greater than or equal to 0 and less than or equal to 1; wherein said water partial pressure is equal to or greater than about 0.4 bar; wherein said bi-layer reactor comprises an outer layer, an inner layer, an outer surface, an inner surface, and an interface between said outer layer and said inner layer; wherein said outer layer is made from an outer layer material, has an outer layer thickness, and extends from said interface to said outer surface; wherein said inner layer is made from an inner layer material, has an inner layer thickness, and extends from said inner surface to said interface; wherein said inner layer material comprises at least one of aluminum, silicon, or mixtures thereof; wherein said inner surface is in contact with said catalyst; and wherein said bi-layer reactor has a corrosion rate lower than about 1.3 mm/y during said dehydration. 
 
     
     
       2. The method of  claim 1 ; wherein said phosphate salt is crystalline; wherein said x is 0 or 1; and wherein said cation is a monovalent cation selected from the group consisting of K + , Cs + , and mixtures thereof. 
     
     
       3. The method of  claim 1 ; wherein said phosphate salt is amorphous and partially-dehydrated; wherein said x is any real number greater than 0 and less than 1; and wherein said cation is a monovalent cation selected from the group consisting of K + , Cs + , and mixtures thereof. 
     
     
       4. The method of  claim 1 ; wherein said outer layer comprises two or more sublayers. 
     
     
       5. The method of  claim 1 ; wherein said outer layer material is selected from the group consisting of stainless steel and carbon steel. 
     
     
       6. The method of  claim 1 ; wherein said inner layer material is selected from the group consisting of aluminum, silicon, and mixtures thereof. 
     
     
       7. The method of  claim 1 ; wherein said inner layer is formed by a bonding process of said inner layer to said outer layer. 
     
     
       8. The method of  claim 7 ; wherein said bonding process is selected from the group consisting of cladding, laser cladding, explosion cladding, electromagnetic fusion cladding, fusion welding, explosion welding, gluing, pressing, rolling, coextrusion, thermal spraying, electroplating, and chemical vapor deposition. 
     
     
       9. The method of  claim 8 ; wherein said bonding process is followed by oxidation of said inner surface when said inner layer material is selected from the group consisting of aluminum, silicon, and mixtures thereof. 
     
     
       10. The method of  claim 1 ; wherein said inner layer material is formed by a dipping process of said outer layer in a bath comprising said inner layer material. 
     
     
       11. The method of  claim 10 ; wherein said dipping process is followed by oxidation of said inner surface when said inner layer material is selected from the group consisting of aluminum, silicon and mixtures thereof. 
     
     
       12. The method of  claim 1 ; wherein said outer layer material is stainless steel; wherein said inner layer material is formed by a dipping process of said outer layer in a bath comprising aluminum and silicon; and wherein said inner surface is subjected to oxidation and forms an oxide-based surface passivating layer comprising alumina and silica. 
     
     
       13. The method of  claim 1 ; wherein said outer layer material is stainless steel; wherein said inner layer material is formed by a dipping process of said outer layer in a bath comprising aluminum; and wherein said inner surface is subjected to oxidation and forms an oxide-based surface passivating layer comprising alumina.